Toxodontidae is an extinct family of notoungulate mammals, known from the Oligocene to the Holocene (11,000 BP) of South America, with one genus, Mixotoxodon, also known from the Pleistocene of Central America and southern North America (as far north as Texas). Member of the family were medium to large-sized, ranging from around 350–400 kg in Nesodon to 1000–1200 kg in Toxodon, and had medium to high-crowned dentition, which in derived members of the group evolved into ever-growing cheek teeth. Isotopic analyses have led to the conclusion that Pleistocene members of the family were flexible mixed feeders (both browsing and grazing).

Taxonomy

The endemic notoungulate and litoptern ungulates of South America have been shown by studies of collagen and mitochondrial DNA sequences to be a sister group to the perissodactyls. In 2014, a study identifying a new species of toxodontid resolved the families' phylogenetic relations. The below cladogram was found by the study: